Assessing abnormal rod photoreceptor activity with the a-wave of the electroretinogram: applications and methods.
The impact of a disease on phototransduction can be assessed by fitting the leading edge of the rod a-wave to high-energy flashes with a quantitative expression. Two parameters of rod receptor activity are obtained, S (sensitivity) and Rm (maximum response). In this study, the meaning of these parameters and examples of conditions that change them were examined. In addition, a new protocol was developed for obtaining these parameters. A set of three to five white flashes were first presented in the dark and then on an adapting field (30 cd/m2). Subtracting the light-adapted responses from the dark-adapted responses yielded isolated rod a-wave responses. A clinical protocol was developed based on a single white flash energy. It is possible to determine whether a disease is producing a change in S and/or Rm with this single flash energy without the use of any equations.
Hood
D C
DC
Department of Psychology, Columbia University, New York, NY, USA. don@psych.Columbia.edu
Birch
D G
DG
D004596:Electroretinography / Q000379:methods*; D006801:Humans; D008954:Models, Biological; D010775:Photic Stimulation / Q000379:methods; D017948:Retinal Rod Photoreceptor Cells / Q000502:physiology*